1. Technical Field of the invention
The present invention relates to a vehicular electric generation control apparatus, which controls an electric generation status of a vehicle electric generator installed on a passenger car or truck, and a related method for detecting an electric generation status.
2. Related Art
Electric generation torque of a vehicle electric generator, driven by an engine, increases with an increase in electric power supplied to a battery and electrical loads installed on a vehicle, resulting in an increase in load of the engine. To address such an issue, an attempt has heretofore been made in the related art to use an AC generator control apparatus operative to control opening and closing states of a throttle valve depending on an electric generation-rate of the vehicle electric generator for thereby stabilizing an idling speed of the engine as disclosed in, for instance, Utility Model Laid-Open Publication No. 60-181200.
With such an AC generator control apparatus, a pulse signal, occurring at a junction point between a field coil of the vehicle electric generator and the electric generation control apparatus (in particular, a switch section for controlling a field current), is outputted from a signal output terminal (terminal F). An external engine controller detects a duty ratio of this pulse signal, enabling the electric generation-rate of the electric generator to be obtained.
Further, with such a control apparatus, a current limiting element is connected between the field coil and the terminal F. This precludes uncontrollable electric current from flowing to the field coil in the occurrence of a short-circuiting failure between a signal line, starting from the terminal F to the external engine controller, and ground to avoid an abnormal increase in an electrical generation voltage. Also, this prevents wasteful electric power consumption caused by current flowing from the battery to the field coil during a halt of the battery, thereby preventing the battery from over-discharging.
Further, a vehicular electric generation control apparatus has heretofore been known including a circuit for controlling a charge alarm lamp and an alarm signal output terminal (terminal L). The vehicular electric generation control apparatus, installed in an engine room, is connected to the charge alarm lamp, mounted on an instrument panel at a position near a driver's seat, using an elongated wiring, directly driving the charge alarm lamp. Since such an elongated wiring is used, consideration should be undertaken for a voltage drop and current capacity of such a wiring in order to ensure a brightness of the charge alarm lamp when turned on. Therefore, the wiring cannot be formed to be thin and light in weight.
To address such an issue, a proposal has been made to provide a vehicular electric generation control apparatus wherein the instrument is formed with a circuit for driving a charge alarm lamp to allow an electric generator side to transmit a signal for controlling the charge alarm lamp for thereby forming the wiring, extending from the electric generator to the instrument panel, in a thin configuration as disclosed in, for instance Japanese Patent Laid-Open Publication No. 10-51976.
Further, carrying out the two related art manufacturing methods intact results in a vehicular electric generation control apparatus arranged to perform separate controls for a field coil and alarm lamp. Therefore, there is a need for driver circuits and signal output terminals in dual systems and signals lines in dual systems. To overcome such an issue, a proposal has been made in the related art to provide a vehicular electric generation control apparatus wherein a plurality of electric generation-status signals are loaded into an external device to incorporate a signal line in a single system as disclosed in, for instance, Japanese Patent Laid-Open Publication No. 2003-79196.
With such a vehicular electric generation control apparatus, information related to an electric generation status (a conducting status of a field winding) and information related to an abnormal status related to an electric generator are transmitted via a signal line. In particular, during normal operation, a duty ratio of an electric generation signal is set to be greater than a value of 10%, providing an external device with notification of the presence of normal operation. Also, during abnormal operation, a signal masking circuit is arranged to set the duty ratio of the electric generation signal to a value less than 10%, providing the external device with notification of the presence of abnormal operation.
However, although the related art disclosed in Japanese Patent Laid-Open Publication No. 2003-79196 can be formed in a simplified signal line, a need arises for additionally providing a signal output driver incorporating a special signal masking circuit. Therefore, the vehicular electric generation control apparatus becomes complicated in structure with the resultant increase in a size of an IC to which circuits are incorporated, causing an issue with an increase in costs.
Further, with such a related art, the signal masking circuit tends to determine a signal for transmission regardless of a turned-off status of a transistor by which electric current flowing through a field winding is controlled. Therefore, although this enables the external device to obtain an abnormal status of the electric generator, causing the occurrence of issues with a loss of information with the resultant lapse in communication.